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Onion Leaf Miner

Photo: L. Donovall, USDA APHIS

Photo: Sven Spichiger, Pennsylvania Department of Agriculture

What are they?

The onion leaf miner (or allium leaf miner) is a fly native to parts of Europe that attacks plants in the Allium genus, which includes onions, garlic, leeks, chives, and more. The larvae chew the leaf tissue in a long trail down the plant, eventually forming a pupa at the end of the trail. Adults will also puncture holes in a plant to feed on the sap that comes out. Infested plants curl and become distorted.

Are they here yet?

No. But they are in North America, having been found in Pennsylvania in 2015.

Why should I care?

The onion leaf miner’s feeding habits increase the risk of infections in a plant and make the plant unsightly. This results in financial losses for farmers.

How do I distinguish them from native species?

While adults can be distinctive, the damage is most notable. Other fly maggots are pests of onions but are larger in size. The combination of damage and pupae are symptoms of concern and should be sent for proper diagnosis. Submit physical samples to your local Washington State University Cooperative Extension office.